Growing Area
The growing areas listed above assume the light bulbs are being used in a fixture
with a reflector.

Primary - Use the area in this column if the grow light will be the main or only source of light for the plants. This includes areas where minimal light comes from windows or standard house/office lights.

Secondary - Use the area in this column if the grow light will be used in a greenhouse or other area that receives direct sunlight for part of the day to supplement the light from the sun.

Heat Output
The chart above uses a combination of the light bulb temperature and the dimensions of the bulb(s).

Bulb

Average Bulb Temperature

.

Bulb

Average Bulb Temperature

T5

100 to 120° F

Incandescent

220 to 260° F

CFL

130 to 180° F

MH/HPS

450 to 550° F

How Long Should Grow Lights Run?

This depends on the type of plant. Foliage plants need about 14-16 hours of light per day. Flowering plants need 12-16 hours of light per day. You should give most plants at least 8 hours of total darkness daily. Try to have the lights on at the same time every day. You can get an automatic timer for your lights to make it easier.

The Electrical Cost to Run a Grow Light System

To get the operating cost per hour for a light, take the lights combined wattage, and divide it by 1000 to get the kilowatts used. Then multiply that number by the amount your electric company charges per kilowatt hour. HID lights will use the number of watts it emits per hour, ie; 600w system will use 600 watts per hour (regardless of spectrum).(light wattage output / 1000)xelectricity cost per kilowatt hour = Operating cost per hour
operating cost per hour x hours used per month = Operating cost per month

I use 400 watt metal halide and use a conversion bulb to run high pressure sodium. I use the metal halide for the veg growth until I get flowers then switch it to the HPS. I really don't notice a difference in growth between the 2 but I do it anyway.

Right now I'm using the metal halides for getting my plants going for outdoors. I have my fluorescent lights all in use starting other plants and needed more light. I have them about 2' above the plants. Just took the photo below. Tomatoes and Virginia Gold Tobacco,

saw your video on building grow light using dryer pipe, what cfl light do you recommend that i can pickup at a hardware store. i need one that will work for tomatoes, peppers, carrots, rasishs and cucumber, and different herbs.

thanks in advance. im new to this. and wanna grow vegatables all year long in basement.

Beefstake will get 6' tall and then some. You'll need a powerful light like a metal halide or high pressure sodium to get enough light for the entire plant. I wouldn't grow anything much bigger than a pepper plant under a cfl. Tiny Tim tomatoes do great under them. Home Depot carried a 68 watt 2700k cfl bulb that was pretty cheap a few years ago and I used that for the flower stage. I'm not sure if they still have it but I'm still using mine.

Right. I just grew red robin tomatoes under 2 42 watt CFL at 6500k throughout the whole grow without switching to 2700K and they still did great. The higher watts will give you more light so that the light will reach the lower leaves better.

You could probably get away with growing lettuce with a T12 is you keep it as close as possible to the plants. Anything like tomatoes and peppers will get leggy and not grow good at all. I use them just for starting seeds.

Got another question. What are your thought on mixing 2700k and 6500k bulbs?I wanna build a few fixtures that will be used to grow both leafy plants and tomatoes pepper and other veggies, in those fixtures I will be using 2-4 200 watt 2700k bulbs and 2-4 200 watt 6500k. Will this cause issues? My hopes are to match solar light as close as possible. I'm assuming this will be more beneficial to all plants I'm growing? So far my tomatoe plant I'm growing is doing well. Many flowers and 14 tomatoes already under two 200 watt 2700k bulbs.